India, Nov. 16 -- At 31, Aravind Srinivas runs Perplexity, a $20 billion AI search startup that has dared to challenge Google's near-total dominance. Recently listed as India's youngest billionaire, Srinivas is in the spotlight as one of technology's most closely watched founders. In an email interview, he reflects on his journey from academia to building one of the world's most valuable startups, discusses the courage required to take on a tech titan, his philosophy on wealth and wisdom, and his views on AI's transformation of the global economy. Edited excerpts.

Four years ago, you were wrapping up a PhD. You now run a $20 billion startup. It must be quite the change. Your reflections on your journey over the last few years?

The thing...